In reverse osmosis machines, the water is pre-treated by being caused to flow through a succession of units, consisting of a sediment filter, a water softener and carbon filters. The pre-treated water is then fed to the reverse osmosis machine where it is purified for its end use.
Periodically, normally during off-peak operations of the machine, timing devices for the pre-treatment devices of the system operate to cause each piece of equipment to go through its regeneration or flushing mode. The system normally causes the flow through the unit to be reversed so that the reverse flow causes the contaminants removed by the unit to be discharged from the system. After the flushing or regeneration, the unit is returned to its normal operation.
In conventional systems, the operation of each unit is automatically timed to flush during an off-peak period, by reversing the flow of the water through the piece of equipment and diverting the effluent to waste.
In a water purification system having a low demand, the reverse osmosis machine may operate with feed water at its normal supply temperature. However, where the demand for purified water is high, efficient operation of the reverse osmosis machine requires that the temperature of the water be heated to about 77.degree. F., which is the optimum temperature for operation of the membranes in the reverse osmosis machine. The temperature of the water is normally elevated by mixing fresh unheated water with heated water in a proportion to achieve a 77.degree. temperature at the input to the reverse osmosis machine. The standard practice is to mix the hot and cold water to adjust the temperature in advance of the pre-treatment units. Thus, the water flowing through the pre-treatment units is controlled as to its temperature to assure 77.degree. water entering the reverse osmosis machine.